1. Field of the Invention
This invention relates to a ball joint used for connecting, for example, a link connecting rod and a motor arm or a pivot arm in a wiper link mechanism for converting turning force of a wiper motor into oscillating movement of a wiper blade, and a method for assembling a ball joint of this kind.
2. Description of the Prior Art
Among the aforementioned ball joints applied to the wiper link mechanism for converting the rotation of the wiper motor into the reciprocative oscillatory motion of the wiper blade, a ball joint is known which is provided with a ball pin fixed to one end of the motor arm secured to a motor shaft of the wiper motor, and a retainer fixed to one end of the link connecting rod and connected with the ball pin through a spherical pair. Furthermore, a ball joint is known which is provided with retainer fixed to the opposite end of the link connecting rod and, a ball pin fixed to a free end of the pivot arm secured to a pivot shaft and connected with the retainer through a spherical pair.
In the aforementioned ball joints, a joint seal made of rubber further disposed between retainer and ball pin for covering the retainer and the ball pin and making the ball joint waterproof because the link mechanism is installed in a position where rain-water or washing water easily splashes. The joint seal is formed in a bottomless sack-like shape having a first aperture to be fitted to the retainer at one end and a second aperture to be fitted to a stem or shank of the ball pin at the opposite end.
In the setting up of the joint seal on the retainer and the ball pin, it is necessary to tightly fit the second aperture of the joint seal on the shank after passing a spherical portion of the ball pin having a diameter larger than that of the shank through the second aperture by enlarging the second aperture, therefore it is not possible to set up the joint seal at the same time of connecting the ball pin with the retainer.
Accordingly, it is necessary to set the second aperture of the joint seal to the shank of the ball pin in advance to the connection of the ball pin and the retainer in order to assemble the ball joint having the aforementioned structure. Also, it is necessary to set the first aperture of the joint seal to the retainer after connecting the ball pin with the retainer, so that there is a problem in that it is not possible to improve efficiency in the manufacturing process of the ball joint.